Author ORCID Identifier

John C. White ORCID iD icon


Physics, Geosciences, and Astronomy

Document Type


Publication Date



Leyva Canyon volcano is an Oligocene (37.3 to 27.1 Ma) trachyte shield volcano whose eruptive and volcaniclastic deposits of rhyolite and trachyte lavas, ash-flow tuffs, lahars, and associated sedimentary rocks comprise the Leyva Canyon Member of the Rawls Formation. The lavas and tuffs originated from vents located near the present-day "Bofecillos vent" in the central Bofecillos Mountains, approximately 5 km west of the Sauceda Ranger Station in Big Bend Ranch State Park in southernmost Presidio County, Texas. The pyroclastic and volcaniclastic units form the distinctive cliffs and caves at the periphery of the Bofecillos Mountains, with the caves developing in the ash-flow tuffs that underlie the most erosionally resistant lahars; these units are the focus of this discussion.

Journal Title

Austin Geological Society Guidebook

Book Title

Geology at the Crossroads—Big Bend Ranch State Park, Presidio and Brewster Counties, Texas